Findings from U.S. Navy Hydrophone Ranges

Abstract

The U.S. Navy maintains several instrumented ranges equipped with large arrays of bottom-mounted hydrophones that are typically used to track undersea vehicles. The major ranges include the Atlantic Undersea Test and Evaluation Center (AUTEC) located in the Bahamas, the Southern California Offshore Range (SCORE) located off San Clemente Island, and the Pacific Missile Range Facility (PMRF) located off the western side of Kauai, HI. Each of these ranges provides tracking arrays covering an area in excess of 1200 km2. These hydrophone arrays are being used to develop marine mammal passive acoustic detection, classification, localization, and density estimation methods. Hardware systems installed at all three facilities allow real-time monitoring of vocalizing marine mammals. Using these systems, Blainville’s beaked whales have been detected at AUTEC and PMRF. Cuvier’s beaked whales have been detected at SCORE and to a lesser extent at AUTEC. These “sonar sensitive” species are present despite the repeated use of sonar. Based on passive acoustics, the movement of these species in response to sonar has been documented. By combining passive acoustic beaked whale and sonar data with AUTEC ship track data, a risk function for Blainville’s beaked whales was developed. In addition, by combining hydrophone with recording tag data, the beam pattern and source level of Blainville’s beaked whale were measured along with the system’s detection function. This enabled the development of passive acoustic density estimation algorithms. These algorithms are being applied to the long-term, in situ monitoring of beaked whale population at all three facilities.